We’ve seen Auroras at Neptune for the first time

For the first time, scientists have discovered infrared auroras that swirl in Neptune’s atmosphere and confirm decades of scientific speculation.

When NASA’s Voyager 2 mission flew by Neptune in 1989, it found the tempting hint of Aurora activity in the ice giant’s clouds. However, scientists are not able to verify the phenomenon at the time when existing instruments were too weak. Now James Webb Space Telescope (JWST) has finally given the power to register them.

“This was really a fulfillment of this year’s expectation,” says Heidi Hammel at the Association of Universities for Research in Astronomy in Washington DC.

Hammel and her colleagues used JWST’s NIRSPEC, a powerful infrared imaging tool, to capture spectroscopic images of Neptune and analysis the different wavelengths of light emitted by the planet. In 2023, researchers used the instrument to detect Infrared Auroras on Uranus. This time it also found them at Neptune.

The pictures also made it possible for Hammel and her team to start constructing a map of Neptune’s magnetic field. This is especially exciting as the planet is known for having some of the most unusual magnetic poles in the solar system.

Unlike Earth, Jupiter or Saturn, Neptune’s magnetic pole is not centered in its rotation scoles. Instead, “they are offset by almost half of the planet’s radius,” says Hammel. As a result, its auroras appear like irregular blobs that are much closer to its equator, across the region where South America sits on the ground.

In addition to discovering Auroras, JWST observations indicate that Neptune’s ionosphere – the layer of charged particles blending some planets – cooled. It is now, on a ring, approx. 10 percent colder than travel 2, which was passed almost 36 years ago. Similar changes have been cleaned on Uranus.

While the authors of the new study are not sure why this cooling happened, they hope their next JWST observation period planned for 2026 will offer more traces.